The present invention relates to a swirl type foreign material removing machine and a method of removing foreign materials by the machine, wherein foreign materials can be effectively removed from a raw material.
There is a swirl type foreign material removing machine for removing foreign materials from a stock or paper raw material by utilizing a centrifugal force and liquid shearing force. One swirl type foreign material removing machine is formed of a casing in a reversed cone shape, and includes an inlet path for a raw material connected tangentially to an upper outer periphery of the reversed cone shape casing, a first outlet for removing foreign materials at the apex of the reversed cone shape casing, and an outlet path for a refined raw material located in the center of a side wall of the casing at a side opposite to the apex of the casing.
The machine is regulated such that a pressure difference between a pressure in the inlet path and a pressure in the outlet path is constant, such as 1.5 kg/cm.sup.2 by opening and closing an inlet valve formed at the inlet path and an outlet valve formed at the outlet path.
However, among the foreign materials contained in the paper raw material, there are materials with heavy specific gravity, such as sand, metal and so on, and materials with light specific gravity, such as wood chips and so on. Also, even if specific gravity is the same, shapes of materials may be different. Thus, in case the pressure difference is controlled to be the same, it is difficult to effectively remove many kinds of foreign materials.
Also, since the inlet valve for adjusting the pressure difference is located away from an opening for the inlet path in the reversed cone casing, the ejecting energy from the opening is consumed by pressure loss and so on from the inlet valve to the opening of the casing. Thus, swirl is not effectively formed in the casing, and large power is required by a pump.
The present invention has been made to obviate the above drawbacks, and to provide a swirl type foreign material removing machine and a method of removing foreign materials by the machine, wherein various foreign materials can be effectively removed.